Mechanism and method for circumscribing oval shapes

ABSTRACT

A mechanism is provided for circumscribing oval paths, wherein a pivotably mounted element is dynamically oriented so as to maintain a functional axis thereof constantly tangent to the circumscribed path. An orienting arm attached to the mounted element is arcuately reciprocated by an element moving unidirectionally in a circle, the direction of circular movement being opposite to that in which the mounted element proceeds.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of copending application Ser.No. 07/429,009, filed Oct. 30, 1989 and now issued as U.S. Pat. No.5,033,346, which in turn is a continuation-in-part of copendingapplication Ser. No. 07/380,217, filed July 14, 1989 and now issued asU.S. Pat. No. 5,014,584, the benefit of the filing dates of which arehereby claimed.

BACKGROUND OF THE INVENTION

Sheets of cardboard mat, glass and other materials are frequently cut toprovide components having openings and/or perimeters of circular orelliptical (generally referred to as "oval") configuration. Suchcomponents are widely used for mounting and framing of pictures and thelike.

Machines are known in the art, and are commercially available, forcutting planar workpieces to such shapes; exemplary is the devicedescribed in Pierce U.S. Pat. No. 4,112,793, issued Sept. 12, 1978.Although the device of the Pierce gatent is highly effective for itsintended purposes, it has an inherent drawback, attributable to themanner by which the cutting blade is mounted.

As is true of virtually all machines of the kind described in the Piercepatent, the blade, supported to permit it to freely swivel, ispositioned to trail slightly behind the axis of pivoting, therebyenabling it to seek an appropriate approach angle. This arrangement isdisadvantageous for several reasons.

Most significantly, such machines are not capable of cutting perfectovals because the blade has a tendency to proceed in a straight line;the deviation from a true elliptical path is particularly noticeablewhen the minor axis of the shape is relatively small compared to itsmajor axis. Secondly, the trailing blade tends to produce an oval that"leans"; that is, the major and minor axes are tilted slightly fromthose of a true Cartesian oval. Finally, such an arrangement results inindefiniteness in the starting and finishing points of the blade, oftencausing those points to be noncoincident, ultimately producingimperfections along the cut.

It is recognized that at least certain of the foregoing deficiencies canbe overcome by dynamically orienting the blade so as to maintain itscutting axis constantly tangent to the elliptical path that isgenerated. A commercially available device that is intended to operatein that general manner utilizes a control arm, attached at one end to apivotable cutter head, which rotates about and follows, at its oppositeend, an oblong cam. The mechanism does not however produce true tangencyat all points of the oval, and it is unsatisfactory for other reasons aswell; perhaps most notably, it employs no associated support, insteadbeing positioned for use simply by fastening it to a base board throughthe workpiece itself.

It will also be appreciated that mechanisms and methods carried out forpurposes other than cutting, and using functional elements suited tosuch other purposes, may also suffer from the deficiences hereinabovedescribed, or that they may simply benefit from the incorporationthereinto of the features set forth herein.

Accordingly, it is the broad object of the present invention to providea novel mechanism, machine and method for circumscribing oval paths.

A more specific object is to provide such a mechanism, machine andmethod in which a functional axis of a pivotably mounted element isdynamically oriented so as to maintain it in a relationship of truetangency to a circumscribed oval path, at all points therealong.

SUMMARY OF THE INVENTION

It has now been found that certain of the foregoing and related objectsof the invention are attained by the provision of a mechanism whichincludes, in combination: means having a first axis, for mounting anelement; means for moving the mounting means along an oval path about acenterline, substantially in a plane; an orientation control system; andmovement transmitting means. The means for moving will include amounting piece and an elongate arm member, the arm member having anouter end portion on which the mounting means is operatively mounted forpivotal movement about a second axis, generally perpendicular to thefirst axis thereof and parallel to the centerline. The arm member willalso have an inner end portion, slidably mounted in the mounting piecefor selectively variable extension therefrom along the longitudinal axisof the arm and in a plane spaced above and parallel to thefirst-mentioned plane.

The orientation control system will comprise a hub, means supporting thehub on the centerline for rotation thereabout, and two parallel slides.One end portion of a first slide will be mounted in the hub forselectively variable extension, radially with respect to the centerlineand perpendicular to it, with the other end portion thereof projectingfrom the hub. The second slide will also have one of its end portionsmounted in the hub; its other end portion will have a coupling componenton it, and will project in the same direction as does the correspondingend portion of the first slide. The control system will further includean elongate orienting arm having one end portion engaged with themounting means, and having its other end portion pivotably engaged withthe coupling component of the second slide, the arm itself beingslidably engaged with either the mounting means or the couplingcomponent.

The transmitting means of the mechanism will transmit movement from themeans for moving to the first slide member, so as to effect rotation ofthe hub about the centerline. It will comprise cooperating componentsoperatively connected to the mounting piece of the means for moving andto the "other" end portion of the first slide member; the componentconnected to the mounting piece will be of selectively variableposition, so as to enable it to follow a circular path about thecenterline during operation of the means for moving. As a result, the"first" axis of the mounting means will thereby be constantly maintainedin a relationship of substantial tangency to the oval pathcircumscribed, as the mounting means moves therealong.

Other objects of the invention are attained by the provision of amachine, which comprises the mechanism hereof in combination with otherfeatures, hereinafter described.

Yet additional objects are realized by the provision of a method forcircumscribing an oval path. The method comprises the steps of moving apivotably mounted element, which has a functional axis, in a givendirection along an oval path, in a plane and about a central axis normalto the plane, the axis of pivotable mounting of the element beinggenerally parallel to the central axis and perpendicular to thefunctional axis thereof; and moving, in the direction opposite to the"given" direction, a drive element along a circular path concentricwith, and in a plane parallel to, that of the oval path. The mountedelement and drive element are moved at the same rate of angular speed,and the circular movement of the drive element is translated intoreciprocating pivotal movement of the mounted element, about the axis ofpivotable mounting, so as to thereby constantly maintain its functionalaxis substantially tangent to the oval path as the mounted element movestherealong. The diameter of the circular path will usually be equal tothe difference between the major and minor diameters of the oval pathcircumscribed. In a specific embodiment, the method is effected forcutting an oval shape in a workpiece, in which case the mounted elementis a blade.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary perspective view of one form of machineembodying the present invention;

FIG. 2 is a fragmentary plan view of the machine of FIG. 1;

FIG. 3 is a fragmentary sectional view of the machine, taken along line3--3 of FIG. 2 and drawn to an enlarged scale;

FIG. 4 is a fragmentary, exploded perspective view showing features ofthe mechanism of the invention by which control of the path of movement,and orientation of the machine cutting head, are achieved;

FIGS. 5A-5E are sequential schematic representations showing anorientation control arm at progressive positions during the cutting ofone quadrant of an oval, in the embodiment of the foregoing Figures, andalso showing geometric elements involved in producing the headorientation control;

FIG. 6 is a fragmentary sectional view, taken along line 6--6 of FIG. 3and drawn to an enlarged scale, showing a cutting head, taken along itsmedial plane, and also showing the support structure therefor, all asemployed in the machine of FIGS. 1-4;

FIG. 7 is a perspective view of the cutting head, with the operatingdial or spool for one of the blades displaced from the supporting wall,for clarity of illustration;

FIG. 8 is a fragmentary elevational view of the cutting head;

FIG. 9 is a fragmentary front elevational view of a clamping systemsuitable for use in machines embodying the invention: and

FIG. 10 is a fragmentary end elevational view thereof.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Turning now in detail to FIGS. 1-4 of the appended drawings, thereinillustrated is a machine embodying the present invention and including arectangular base board 10 yieldingly supported upon a pair of U-shapedrunners 12, the base board being secured thereto by nut and boltfasteners 16 (one of which is shown in FIG. 3) with a small conical coilspring 18 interposed therebetween. A stand, generally designated by thenumeral 14, is secured to the rear ends of the runners 12 by fastenerspassing through flanges 20 at the lower ends of legs 22, and an overheadsupport arm, generally designated by the numeral 26, is bolted to theupper crosspiece 24 of the stand 14, to project forwardly therefrom overthe base board 10.

A slot 28 extends along the longitudinal axis of the arm 26 in theforward, free end portion thereof. Two parallel, rectilinear gibs 30(normally made of a low-friction synthetic resinous material, such aDelrin) are secured to the upper surface of the arm at the opposite endsof the slot 28. The gibs have smooth inner surfaces, and one of them maybe formed with oversized holes for receipt of the screws 32 with whichit is held in place on the arm 26, so as to permit fine adjustment toattain strict perpendicularity to the axis of the slot 28. Although notillustrated, the upper surface of the arm 26, in the area between thegibs 30, will normally have a low-friction surface component thereon,such as may be provided by a suitably configured plastic coveringwasher.

An upper disk, generally designated by the numeral 34, is disposed onthe top surface of the arm 26 with its circumferential edge bearing uponthe inside surfaces of the two gibs 30. It has a slot 36 therethroughformed along a diametric axis and extending essentially to one side ofthe center of the disk; a distance scale 38 is provided adjacent theslot 36.

A center shaft assembly is rotatably and slidably received within theslot 28 of the arm 26, and includes a cylindrical center shaft corepiece 40 carrying a cylindrical plastic bushing 42, dimensioned to spanthe slot 28 and to closely engage its lateral surfaces. A lower disk 44is attached to the core piece 40 by a screw 46, with a plastic washer 45interposed therebetween, and the components are affixed against relativerotation by pins 50. The upper end of the core piece 40 has adiametrically extending tongue element 52, the parallel side surfaces ofwhich slidably engage the lateral surfaces of the slot 36 of the upperdisk 34. Extending axially through the core piece 40 is a threaded bore54, at the upper end of which is engaged the threaded shank 56 of aclamping knob 58, and at the lower end of which the screw 46 is engaged.A U-shaped clamping block 60 is disposed on top of the disk 34, and hasa channel 62 extending through it within which the tongue element 52 ofthe core piece 40 is received.

The operating handle, generally designated by the numeral 65, consistsof a bar 64 with a knob 66 rotatably mounted on one end and with anaperture 68 through its opposite end, the latter receiving the shaft 56of the clamping knob 58 (with a washer 57 interposed under the head), tothereby attach the handle to the center shaft assembly. The clampingblock 60 mounts a laterally extending, transparent indicator piece 70,disposed over the scale 38 so as to permit setting of the center shaftassembly at any selected point along the length of the slot 36; thefirst line on the scale, nearest the center of the disk, lies at thegeometric center thereof. It should be noted that the components are ofsuitable lengths and thicknesses to ensure that the upper disk 34 willbe clamped between the block 60 and the core piece 40 when the knob 58is tightened, to affix the center shaft assembly to the disk whileleaving both free to move relative to the support arm 26.

As will be appreciated by those skilled in the art, the mechanismhereinabove described employs the "Scottish yoke" principle, which isalso embodied in the machine shown in the above identified Pierce U.S.Pat. No. 4,112,793. It serves to permit generation of elliptical shapes,each with a major axis that varies from its minor axis by a dimensionthat is determined by the setting of the center shaft assembly relativeto the center of the disk, at an "offset" value. To the extent that itmay be helpful to an understanding of the form and operation of theScottish yoke mechanism employed herein, the specification of theaforesaid said Pierce patent is incorporated hereinto by reference.

An extruded metal (e.g., aluminum) housing, generally designated by thenumeral 72, is secured (by screws, not shown) to the lower disk 44 ofthe center shaft assembly, and has a downwardly opening compoundpassageway 74 therethrough, which is configured to slidably mount acutter arm, generally designated by the numeral 76, and a transmissionslide, generally designated by the numeral 78. A distance scale 80 isprovided along the length of the cutter arm 76, and a clamping screw 82extends through the wall of the housing 72 and into the passageway 74;it cooperates with a shoe (not seen), which bears upon the side of thecutter arm 76 opposite to that on which the scale 80 is provided, so asto secure the arm in any selected position of extension.

The transmission slide 78 is similarly engaged in selected positions ofextension from the housing 72 by use of the locking screw 84. A pin 86,fixed adjacent one end of the slide 78, projects downwardly through theopen bottom of the passageway into engagement in a circular socket 88(normally lined with a press-fit bushing) formed into one end of ahalfscale slide 90; a half-dog set screw 94 is affixed to the oppositeend of the slide 90, and a distance scale 92 extends longitudinallyalong one of its side surfaces.

A hub assembly consisting of two substantially identical pieces, eachgenerally designated by the numeral 96, is disposed beneath the housing72. Hub piece 96 consists of a circular base portion 98 providing acircumferential shoulder 100 thereabout, and a pair of projectingparallel walls 102 define a channel 104 between them. A cover plate 106is secured over the channel 104 on the end faces of the walls 102 byfour screws 108, and the plate is notched at 110 for a reason that willbe clear from what follows.

The hub pieces 96 are affixed to one another with the faces of the baseportions 98 in confronting contact and with the channels 104 thereof inalignment; they are held together by screws (not shown) engaged withinthe apertures 112. The shoulders 100 cooperate to form a circumferentialgroove, by which the assembly is rotatably mounted in the circularopening 114 of an angular mounting bracket, generally designated by thenumeral 116; it should be noted that the hub assembly is therebypositioned to rotate on its own axis, coincident with the centerline ofthe machine.

The half-scale slide 90 is slidably engaged within the channel 104 ofthe uppermost hub piece 96, the half-dog set screw 94 carried therebyserving to limit extension and thereby to prevent inadvertentdisassembly; as can be seen, the tip of the screw 94 is seated withinthe slot 118 formed into the inner surface of the disk portion 98. Themated hub piece 96 slidably engages an actuating full-scale slide 120,which has a scale 122 along lateral surface and which carries dependingpin 124 at its outer end. It should be noted that the actual distancebetween the integers (and the graduations) of the scales 38, 80 and 122,on the upper disk 34, the cutter arm 76, and the full-scale slide 120,respectively, are the same, whereas the corresponding distances on thescale 92 of the half-scale slide 90 are half those values. The distancesshown on the scales 38, 92 and 122 are representative of the offset (ininches) that is to be produced; the distances shown on the scale 80 arerepresentative of the minor diameter value that the oval is to have. Thefull-scale slide 120 is held in selected positions by use of lockingscrew 84, which is threadably engaged within the wall 104 of the lowerhub piece 96; the half scale slide 90 is held in position by virtue ofits connection through pin 86 to the transmission slide 78.

Secured to the underside of the supporting arm 26 are four rollers 126,which are circularly disposed, at suitable intervals, relative to themachine centerline. The rollers 126 engage within their circumferentialgrooves 128 the outer marginal edge of a support ring 130, for rotationunder the arm 26. Two posts 132, separated by 120°, are attached to thering 130, and they in turn support the angle bracket 116, the ends ofthe bracket arms 134 being provided with apertures for the receipt ofscrews 138 for that purpose. As previously noted, the support system isso constructed as to position the center of the circular opening 114 inthe angle bracket 116 (and thereby the axis of rotation of the hubassembly) on the centerline of the machine (as so designated in theFigures). The centerline constitutes an axis extending normal to theparallel planes of the upper surfaces of the support arm 26 and the baseboard 10, at the intersection of the slot 28 with an imaginary medialline extending parallel to the confronting surfaces of the gibs 30,halfway therebetween.

A pin 140 extends downwardly from the ring 130 at a point equidistantlyspaced from the posts 132. Bracket 142, attached by screws 144 againstthe top wall of the housing 72, extends therefrom within a longitudinalchannel 146 formed along the tog of the cutter arm 76. The bracket 142is slotted lengthwise to slidably receive the pin 140 that depends fromthe ring 130, as a result of which the ring is rotated by action of thecutter arm 76, so as to avoid interference between the arm and the posts132 that support the bracket 116.

With additional reference now to FIGS. 6-8, the cutter head assembly,mounted upon the free outer end of the cutter bar 76, includes anF-shaped bracket, generally designated by the numeral 150. The laterallyextending elements 152, 154 of the bracket are formed with verticallyaligned openings 156, 158, within which are seated, respectively, abushing 160, having an upper retaining flange portion 161, and a bearingsleeve 162.

A mounting post has an enlarged head portion 164 abutted against thebottom surface of the cutter arm 76, and is secured thereto by a screw166 engaged within its threaded bore 167. The post has tworeduced-diameter cylindrical bearing portions 168, 172, which serve topivotably support the bracket 150, and a threaded intermediate portion170 therebetween. The threaded portion 170 engages a knurled collar 174,which bears upon the bushing flange portion 161 and is turned to effectadjustment of the vertical position of the bracket 150 on the mountingpost.

The cutter head assembly is mounted upon the vertical leg portion 176 ofthe bracket 150, and includes a body having a lateral wall portion 178and a base block 180, the leading lower marginal portion 181 of which iscovered with a piece 183 of low-friction tape. A medial channel 182extends along the back surface of the wall portion 178, and slidablyengages the leg portion 176 of the bracket to ensure proper orientationof the cutter head, the assembly being maintained by engagement of thescrew 186 within the threaded aperture 189.

The base block of the cutter head, which is symmetrical about a medialplane extending vertically through the aperture 189, extends laterallyfrom the wall portion 178 and has downwardly converging surfaces 190 onopposite sides thereof (which are, as will be discussed more fullybelow, slightly divergent, as well). Secured to each of the surfaces190, by use of screws 192, is a guideplate 194, the inside surface ofwhich is indented at 196 to define a channel in cooperation with theconfronting surface 190. The plates 194 are confined by an outer wallportion 198 on the base block 180.

A flat, planar cutting blade 200 is slidably engaged within each of thechannels 196, and has a sharpened bottom edge defined by surfaces 201,and an aperture 202 through the top end thereof. A set screw 204 extendsthrough the plate 194 to bear upon the blade 200, creating (whenproperly adjusted) frictional resistance to help maintain the blade inany selected position within the channel 196 while permitting readymovement thereof when desired, and also helping to permit manufacturewith tolerances of practical magnitude.

The reason for the slight divergence of orientation, mentioned above, isto compensate for the fact that the blades enter the mat atnon-perpendicular angles thereto, and to achieve full line contactbetween the outside surface 201 of the cutting edge (which is of courserectilinear and bevelled relative to the plane of the blade itself) andthe cut produced in the workpiece; i.e., to provide as perfectly tangenta relationship as is feasible, and thereby to produce a virtuallyflawless cut edge regardless of the point of entry or withdrawal of theblade. Consequently, and although not visible in the drawings, thesurfaces 190, 196, defining the channels in the base block of the head,are such that the planes of the blades are canted outwardly thereby,typically at an angle of about 5° (which is determined by resolution ofthe compound angular relationship presented by the several components),causing the blades to diverge from one another in a forward direction(i.e., toward the leading end of the head). As will be appreciated,reference to "outside" surfaces refers to the surfaces that areoutermost with respect to the cutting head, one of which outside surfacewill of course run along the more inward of the lateral surfacesdefining a cut edge or a V-groove. It will also be appreciated that thedivergence described will dispose the rectilinear axes of the outsidesurfaces 201 of the cutting edges of the two blades parallel to oneanother.

Associated with each blade 200 is a positioning dial or spool, generallydesignated by the numeral 206, and consisting of a circular base portion208 and cylindrical barrel or handle portion 210. A passageway 212extends through the spool, and receives a mounting screw 214, thethreaded end of which is engaged in a threaded aperture 216 in thelateral wall portion 178 of the cutter head body. The passageway 212includes an enlarged diameter outer section 212', with a circumferentialshoulder formed at the inner end thereof. One end of a coil spring 218is seated upon the internal shoulder, and the opposite end thereof bearsupon the head of the screw 214, thereby creating a biasing force ofadjustable strength to displaceably maintain the spool against the wallportion 178. Adjacent the aperture 216 is a semi-circular slot 220,within which is engaged a short pin 222 extending from the inner face ofthe circular base portion 208 of the spool; this serves of course tolimit rotation.

A small pin or finger 226 extends radially from a tapered intermediatesection 224 of the barrel portion 210, which is engaged within theaperture 202 in the top end of the associated blade 200. As will beself-evident, turning of the positioning spool will serve to raise andlower the coupled blade, to an extent limited by the corresponding slot220, so as to cause the cutting element thereof to move up and downthrough the bottom plane of the cutting head (i.e., the plane in whichthe lower surface of the marginal portion 181 and the tape piece 183reside). The biasing force of the spring 218 will help to maintain thespool (and thereby the blade) in position, and the blade can be removedentirely from the head by disengagement of the finger 226 on the spoolfrom its aperture 202. This is readily done by withdrawing the spoolaxially against the force of the spring 218, to disengage the pin 222from the slot 220 and thereby permit rotation past the fully retractedposition of the blade, as necessary to effect the desired disengagement.It will be noted that the edge of the wall portion 178 has a scale 228on each shoulder, which cooperates with the indicating line 231 on thecircumference of the spool base portion to permit reproducibleadjustment of the extent of projection of the blade 200 beyond thebottom face 296 of the head.

An orientation control arm, generally designated by the numeral 230, isrigidly attached at one end (as by use of screws, not illustrated) tothe underside of the lower bracket element 152, and extends laterallytherefrom toward the center of the machine. A slot 232 is formed alongmost of the length of the arm 230, and engages the pin 124 that dependsfrom the full slide 120.

Centrally mounted at the rear of the stand 14 of the machine is alocking block 236, having a channel in which is slidably received thetail piece 234 of a T-bar. The tail piece 234 has a distance scale 240extending longitudinally along an upper surface, and the locking block236 has a thumb screw 242 extending through it and through a clampingshoe (not visible) for securing the tail piece, and thereby thecrosspiece 238 attached to its forward end, in any selected positionover the base board 10. An inverted, U-shaped clamping member 244 isdisposed over the crosspiece 238, and is substantially coextensivetherewith.

Identical clamping mechanisms are provided at the opposite ends of thecrosspiece and clamping member. Each consists of an L-shaped clamp head246, having a nose portion 248 engaged under the base board 10 and aneck portion 250 seated within the space between the forward andrearward walls 252, 254 of the clamping member. Extending throughaligned bores 256, 258 in the clamp head 246 and the crosspiece 238,respectively, and through an aperture 260 in the top wall 262 of theclamping member, is a rod 264 having a threaded lower end 266 and atransverse pin 268 through its upper end.

An operating lever, generally designated by the numeral 270, isassembled with the rod 264, and includes a handle portion 272 and headportion, the latter comprising sidewalls 276 and an internal element274, providing arcuate bearing surfaces 278; the opposite ends of thepin 268 are engaged within the sidewalls 276. A nut 280, having aknurled knob thereon, is threadably engaged on the end 266 of the rod264, and is seated within the clamp head 246. Interposed between the topwall 262 of the clamping member 244 and the upper surface of thecrosspiece 238 is a coil spring 282. A small pin 284 (or preferably, ashoulder screw) projects rearwardly from the crosspiece 238, and isengaged within a slot 286 formed through the back wall 254 of theclamping member. The front wall 252 thereof is formed with a rib 288,below which is defined a dovetail groove 297 extending longitudinallytherealong; the internal arcuate surface 278 of the lever 270 bears uponthe top wall 262.

As will be apparent, in preparation to cut a workpiece such as the matsheet 290 shown in the drawings the T-bar is initially positioned in thelocking block 234 so as to properly locate the mat on the base board 10(the latter normally having a slip sheet or covering sheet 291 thereuponfor optimal utility). The clamping member is provided with a distancescale 298 along its forward wall portion 252, to permit ready centeringof the workpiece, and an adjustable measuring stop (not shown) may beslidably mounted in the dovetail groove 297, if so desired, to furtherfacilitate positioning with the clamping member 244 in its elevatedposition (as shown in the several Figures), a marginal portion of themat 290 can be inserted beneath the lower edge 294 of the front wallportion 252 to abut against the forward face of the crosspiece 238.Elevating the handle portions 272 of the operating levers 270 will causethe underlying contacting surface (which may have a strip ofhigh-friction and/or cushioning material applied thereto) of theclamping member 244 to be forced downwardly (by the action of thearcuate surfaces 278 upon the cooperating elements), thereby causing theedge surface to tightly grip the marginal portion of the mat 290.

Different thicknesses of workpieces can readily be accommodated byadjustment of the height of the clamping member 244. This isaccomplished simply by tightening or loosening of the nuts 280, therebyraising or lowering the clamping member, as necessary.

To commence the cutting operation, the cutter arm 76 will be extendedfrom the housing 72 a distance corresponding to the minor axis of theoval shape that is to be cut, utilizing the scale 80 thereon (which maybe read directly to indicate the minor diameter). The knob 58 isloosened to permit shifting of the upper disk 34 (which would normallybe done with the handle rotated 90° from the position shown in FIG. 1,so as to align the slot 36 with the gibs 30) to establish the desiredoffset, utilizing the indicator 70 in cooperation with the scale 38 onthe disk 34; the sum of the offset value plus the cutter arm extensionreading will equal the value of the major diameter of the oval to becut. The coupled transmission bar 78 and the half-scale slide 90 arealso extended from the housing 72 and the upper hub piece 96,respectively, to provide the same offset reading on the scale 92 as isindicated on the scale 38; the actuating slide 120 is extended from thelower hub piece 96 in which it is mounted, once again to provide thesame offset reading on the scale 122.

The knurled collar 174 is thereafter rotated so as to bring the tapecovered face 296 of the cutter head into sliding contact with the mat290 (the tape 183 serving of course to promote sliding thereupon, and toprevent scuffing of the surface). Depending upon whether the mat isbeing cut from what is to be its front or its rear surface, one or theother of the blades 200 will then be extended as necessary to producethe desired degree of penetration, by turning of the associated spool206.

Moving the handle 65 (in a counterclockwise direction) will of coursecause the disk 34 and the center shaft assembly to rotate in the samedirection. Due to the constraints imposed by the gibs 30 however, thecenter shaft assembly will be forced to slide along the slot 28 in theupper support arm 26, while the disk migrates back and forth along anaxis parallel to the faces of the gibs. This will superimpose theestablished offset distance upon the otherwise circular path of thecutter head 150, thereby causing it to circumscribe an oval. (As will beself-evident, if the center shaft assembly were positioned at the centerof the disk 34 the resultant shape would be that of a circle, since nooffset would be imposed.)

As the center shaft rotates on its own axis, and simultaneously movesback and forth through the centerline of the machine, the geometry ofthe system (with the slides set as described) will cause the pin 86 onthe transmission bar 78 to follow a circular path, in a clockwisedirection (i.e., opposite to the direction of rotation of the disk 34).As a result, the hub assembly will rotate in the same direction withinthe center bracket 116, in turn causing the pin 124 to move clockwiseand to circumscribe a circular path.

Rotational movement of the pin 124 (following its circular path) withinthe slot 232 of the orientation bracket 230 will translate to areciprocating pivotal action to the cutter head 150. Again due togeometric principles (which will be discussed hereinbelow), pivoting ofthe head under such control will constantly maintain the cutting (i.e.,the functional) axis of blade 200 in a relationship of true tangency tothe oval path being followed, thereby producing a virtually perfect cutin the mat 290.

To enable the pin 86 to move in a circle, in response to the compoundmovements of the center shaft assembly, it is necessary that the radiusof the path circumscribed by the pin 86 (taken from the centerline ofthe machine) be exactly onehalf the value of the offset distance set onthe scale 38. To facilitate that, the actual distances between indiciaon the scale 92 on the half-scale slide 90 are one-half those that areprovided between common indicia on the scale 38; thus, one need only setthe cooperating parts at the same integer or graduation markings on thescales to achieve the required relationship. The distances on the scale122 of the actuating slide 120 are the same as those on scale 38, tofacilitate setting of the slide so as to enable the pin 124 to follow apath (about the centerline) having a radius equal to the offsetdistance, as is necessary to produce the required orientation controlfor the cutter head. As noted previously, the markings on the scale 80denote minor diameter lengths, and so the actual distances betweenintegers are half of the values indicated.

The cutting head employed on the machine can readily be utilized forso-called "V-grooving" of mat board. To do so it is simply a matter ofmaking a first cut with one of the blades in operative position, andthereafter making a second cut, along the same path, utilizing the otherblade. As has been noted, the surfaces of the base portion against whichthe blades are mounted converge at an angle suitable to cause the bladesto produce, by their cooperative action, a V-shaped cut.

It might also be emphasized that the mechanism, machine, and method ofthe invention, and the underlying concepts, are applicable not only forcutting or scoring of workpieces such as mat board, plastic and glass,but also for performing other operations (e.g., grinding, milling,optical inspection, etc.) on, or with respect to, any of numerous kindsof workpieces; thus, the term "circumscribed" is used in a broad senseherein, to encompass all of such operations. Different forms of mountingmeans and elements, appropriate to the material of the workpiece and tothe function that is to be carried out, will of course be employed andwill depend upon the nature of the particular application involved. Asanother example, a cutting head body could be fitted with an embossingwheel, to add desired aesthetics to the workpiece; such a wheel isconventionally formed with a rounded circumferential edge cross section,and is used to impress an indentation in the surface of a mat boardalong the travel path of the head.

Turning finally to FIGS. 5A-5E of the drawings, therein illustratedschematically and sequentially is the manner in which the cutter headorienting bracket, or other mounting means of the instant mechanism,moves while circumscribing one quadrant of an oval, so as to control itsorientation and thereby maintain the blades, or other mounted element,with functional axes thereof in relationships of precise tangency.Needless to say, an axis of the mounting means, parallel to thefunctional axis of an operative element, will simultaneously bedynamically maintained in such tangential relationships. The Figuresalso illustrate the geometric principles underlying the operation of themachine illustrated. (It should be noted that the directions of movementare arbitrarily chosen to be opposite to those entailed in the machineembodiment hereinbefore described.)

As the cutting head moves along an oval path "f", the locus of a point"C" on the axis of the cutter bar 76 (the bar axis being represented bythe dash line "1" in these Figures) is a circle "c" generated in thedirection opposite to that in which the cutter head proceeds.Orientation of the cutter bar is controlled by constraining points A andB (separated by the offset distance) on its axis to movement onperpendicular y and x axes through the point "O" at the center of themachine (and hence at the center of the oval shape "f" generated); point"A" corresponds to the rotational axis of the center support assembly ofthe machine, and point "B" may be considered to be the geometric centerof disk 34, which follows an imaginary point on the axis of the cutterbar moving along an axis midway between the confronting gib surfaces.Since the pin 86 of the machine is positioned at point C, midway betweenpoints A and B, it generates the circle "c" having a radius equal tohalf the offset distance.

In the Figures, the diameter of circle "a" corresponds to the minordiameter of the oval "f", and the radius of circle "b" equals themachine offset distance. Adding the diameter of circle "b" to the minordiameter circle "a" provides the major diameter of the oval,corresponding to the diameter of circle "d"; circle "e" is drawn to havethe diameter of tangency, equal to the sum of the major and minordiameters. For example, setting the cutter bar to provide a six-inchminor diameter, and setting the upper disk to provide a two-inch offset,will produce an ellipse with an eight-inch major diameter. If the sameoffset value is set on the scales 92 and 122, the locus of pin 86 willbe a two-inch diameter circle, and that of pin 124 will be a circlehaving a four-inch diameter.

As can be seen, and by way of explanation of the theory of operation ofthe mechanism, a line "2" drawn through point D on the offset radiuscircle "b", and point E on the tangency circle "e", will beperpendicular to a line of tangency "3" at all points on the oval "f".Consequently, disposing the arm 230 between the cutter head bracket 150and the pin 124 (the latter corresponding to point D, at the offsetdistance and aligned on an axis "4" through the center point "O" andpoint "C") will impart the desired, always-tangent orientation to theaxis of cutting of blade 200. It will be appreciated that the alignmentof points "O", "C" and "D" on the axis "4" is produced in the machine bythe relationships of the half-scale and full-scale slides 90, 120 in thehub assembly.

Point "E" on the tangency circle "e" lies at the intersection of a linedrawn parallel to the axis "1" of the cutter bar through the centerpoint "O". The cutting blade 200 is located at the intersection of lines"6" and "7", drawn parallel to the y and x axes of the machine frompoints F and G, respectively; points "F" and "G" lie at theintersections of line 5 with minor and major diameter circles "a" and"d". (It will be noted that some of the reference lines and points havebeen omitted from certain Figures, for clarity of illustration.)

As will be appreciated, the dynamic position of point D will reside atthe intersection with circle "b" of a line through point A drawnparallel to the x axis, and also of a line through point B drawnparallel to the y axis, the intersection of both lines with circle "b"serving of course to locate point D in the groper quadrant. Theforegoing geometric factors can readily be applied in the design of amechanism having the unique true tangent characteristic hereindescribed; it is not believed that these principals have heretofore beenrecognized, or so applied.

Thus, it can be seen that the present invention provides a novelmechanism, machine and method for circumscribing oval paths. Morespecifically, in the mechanism, machine and method the functional axisof a pivotably mounted element is dynamically oriented so as to maintaintrue tangency of that axis to any circumscribed oval path, at all pointstherealong.

Having thus described the invention, what is claimed is:
 1. A mechanismfor circumscribing an oval path, comprising in combination:(a) mountingmeans for mounting an element, said mounting means having a first axis;(b) means for moving said mounting means along an oval pathsubstantially in a plane and about a centerline, said means for movingincluding a mounting piece and an elongate arm member, said arm memberhaving an outer end portion on which said mounting means is operativelymounted for pivotal movement about a second axis generally perpendicularto said first axis and parallel to said centerline, and having an innerend portion slidably mounted in said mounting piece for selectivelyvariable extension therefrom, along the longitudinal axis thereof and ina plane spaced above and parallel to said first-mentioned plane; (c) anorientation control system, comprising:(1) a hub; (2) means supportingsaid hub on said centerline for rotation thereabout; (3) a first slidehaving opposite end portions, one of said end portions being mounted insaid hub for selectively variable extension therefrom, radially withrespect to said centerline and perpendicular thereto, with the other endportion of said first slide projecting from said hub; (4) a second slidehaving opposite end portions, one of said end portions being mounted insaid hub in the same manner as said first slide and parallel to saidfirst slide, the other of said end portions of said second slide havinga coupling component thereon, said other end portions of said first andsecond slides both projecting in the same direction from said hub; and(5) an elongate orienting arm having opposite end portions, one of saidend portions of said arm being operatively engaged with said mountingmeans, and the other of said end portions of said arm being pivotablyengaged with said coupling component of said second slide, saidorienting arm being slidably engaged with one of said mounting means andsaid coupling component; and (d) means for transmitting movement fromsaid means for moving to said first slide member so as to effectrotation of said hub about said centerline, said means for transmittingcomprising cooperating components operatively connected to said mountingpiece of said means for moving and to said other end portion of saidfirst slide member, one of said components connected to said mountingpiece being of selectively variable position so as to enable it tofollow a circular path about said centerline during operation of saidmeans for moving; whereby, as said mounting means moves along an ovalpath said first axis may be constantly maintained substantially tangentto said path.
 2. The mechanism of claim 1 wherein said means fortransmitting further comprises a third slide, slidably mounted in saidmounting piece for movement of said one cooperating component of saidmeans for moving along an axis parallel to said longitudinal axis ofsaid arm member.
 3. The mechanism of claim 1 wherein said first andsecond slides both have scales thereon for indicating the distance ofextension thereof, said slide scales having indicia thereon in common,with the indicia on said first slide scale being spaced half the actualdistance of that o; said common indicia on said second slide scale.
 4. Amachine for causing an element to circumscribe an oval path comprising,in combination, the mechanism of claim 1; a base having a flat uppersurface in a plane parallel to said first-mentioned plane; a frameunited with said base; and an overhead support member on said frame,said support member having a plate portion overlying said base uppersurface.
 5. The machine of claim 4 wherein said plate portion has arectilinear slot therethrough traversing said centerline, and hasconstraining means thereon for constraining a circular componentdisposed on said plate portion to rectilinear movement along an axis ofreciprocation that is perpendicular to the axis of said slot and thatalso traverses said centerline, said means for moving additionallyincluding:(1) a circular component slidably disposed on said plateportion of said support member and movable along an axis ofreciprocation under the constraint of said constraining means, saidcircular component having an elongated slot therethrough extendingdiametrically and traversing the center thereof; (2) a center shaftassembly including a shaft component slidably engaged within saiddiametrical slot, and means for disengagably affixing said shaftassembly against movement relative to said circular component atselectively variable positions along the length thereof, said shaftcomponent also being slidably and rotatably engaged within said slot ofsaid plate portion, and being adapted to effect rotary motion of saidcircular component and lineal motion thereof along said axis ofreciprocation, when affixed thereto; and (3) driving means for effectingrotation of said center shaft assembly, said mounting piece beingoperatively connected to said shaft assembly for movement therewith. 6.The machine of claim 5 wherein said driving means comprises a handlewith a bar attached adjacent one end to said center shaft assembly, andhaving manual gripping means adjacent the opposite end, said bar havinga longitudinal axis aligned with the longitudinal axis of said elongatearm member and being disposed thereover, said one end of said bar beingdisposed to the same side of said shaft assembly as said outer end ofsaid arm member.
 7. The machine of claim 4 wherein said means forsupporting said hub comprises a bracket assembly operatively supportedby said frame to dispose said hub at a level between said overheadsupport member and said base.
 8. The machine of claim 7 wherein saidbracket assembly is rotatably mounted on said overlying plate portion ofsaid frame, and wherein said machine includes driving means operativelyengaged with said bracket assembly and said elongate arm member forrotation thereof at the same angular rate so as to avoid interferencebetween any component of said bracket assembly and said arm member. 9.In a method for circumscribing an oval path, the steps comprising:movinga pivotably mounted element, having an axis of pivotable mounting andhaving a functional axis, in a given direction along an oval path in aplane and about a central axis normal to said plane, said axis ofpivotable mounting of said element being generally parallel to saidcentral axis and perpendicular to said functional axis: moving, in thedirection opposite to said given direction, a drive element along acircular path concentric with and in a plane parallel to that of saidoval path, said mounted element and said drive element being moved atthe same rate of angular speed; and translating the circular movement ofsaid drive element into reciprocating pivotal movement of said mountedelement, about said axis of pivotable mounting, so as to constantlymaintain said functional axis substantially tangent to said oval path assaid mounted element moves therealong.
 10. The method of claim 9 whereinsaid oval path has a major and a minor diameter, and wherein thediameter of said circular path is equal to the difference between saidmajor and minor diameters.
 11. The method of claim 9 wherein saidmounted element is a cutting element and said functional axis is theaxis of cutting thereof, said method being effected for cutting an ovalshape in a workpiece disposed in said plane.